1. Field of the Invention
The present invention relates to a reproducing apparatus and method for reproducing signals from a recording medium onto which a plurality of tracks are recorded using one or a plurality of reproducing heads.
2. Description of the Related Art
In magnetic recordings and reproductions in recent years, an additional increase in a recording density is demanded along with an increase in a capacity of magnetic recording systems. However, if a track width is narrowed so as to obtain a high recording density, there is a problem that it becomes difficult to obtain sufficient tracking performance at a time of the reproduction. In this regard, a non-tracking system capable of reading a signal from a track even when a position of a reproducing head is somewhat deviated from the track is proposed. For appropriately obtaining a reproduction signal in the non-tracking system, however, a strict restriction is placed on a setting of the reproducing head. Thus, there has been a limit in increasing the recording density by narrowing the track width.
In this regard, the inventors of the present invention have proposed a system in which a plurality of tracks that constitute one unit of signal processing for detecting data are recorded onto a magnetic recording medium using a recording head, a plurality of signals with respect to the plurality of tracks are reproduced with different positional relationships with respect to the plurality of tracks using a reproducing head capable of reproducing signals across the plurality of tracks at a time of the reproduction, and reproduction signals are combined as one unit and subjected to signal processing to thus generate a reproduction signal of each track (see, for example, Japanese Patent Application Laid-open No. 2007-265568; hereinafter, referred to as Patent Document 1). With this structure, it is possible to relieve restrictions in determining a width of the reproducing head, narrow a track width, and increase a recording density (see, for example, Patent Document 1).
FIG. 32 is a diagram showing a structure of a recording apparatus 800 that employs the magnetic recording/reproducing system described above.
As shown in the figure, the recording apparatus 800 is constituted of a multitracking section 110, a multitrack recording encoding section 120, a multitrack preamble adding section 130, a multitrack recording section 140, and a recording head array 150.
The multitracking section 110 is constituted of a data distributor 111 that divides recording data 1 into pieces of data corresponding to the number of recording heads W-1, W-2, and W-3 provided to the recording head array 150 for multitracking.
The multitrack recording encoding section 120 is constituted of M recording encoding sections 121-1, 121-2, and 121-3 that encode the M pieces of recording data divided by the data distributor 111.
The multitrack preamble adding section 130 is constituted of M preamble adding sections 131-1, 131-2, and 131-3 that add a preamble specific to each track to the corresponding recording data encoded by the multitrack recording encoding section 120.
The multitrack recording section 140 is means for recording onto the recording medium a recording code string of each track to which the preamble has been added. More specifically, the multitrack recording section 140 is constituted of M output timing setting sections 141-1, 141-2, and 141-3 that each impart a desired timing to the recording code string to which the preamble has been added, M recording compensating sections 144-1, 144-2, and 144-3 that carry out recording compensation processing, and M recording amplifiers 147-1, 147-2, and 147-3 that drive the recording heads W-1, W-2, and W-3, respectively, based on the recording code strings that have been subjected to the recording compensation processing.
FIG. 33 is a flowchart showing a unit recording operation of the recording apparatus 800. In the recording apparatus 800, the multitracking section 110 first divides input recording data 1 into pieces of data corresponding to the number of recording heads W-1, W-2, and W-3 (M=3), that is, pieces of data corresponding to the number of tracks that constitute a unit (Step S801).
The divided pieces of data are encoded into code strings that take into account recording/reproduction characteristics of a magnetic recording medium 2 in the recording encoding sections 121-1, 121-2, and 121-3 of the multitrack recording encoding section 120. At this time, information necessary for data demodulation, such as a synchronization pattern for demodulation, is added to the code strings of the data (Step S802).
Next, in each of the preamble adding sections 131-1, 131-2, and 131-3 of the multitrack preamble adding section 130, a pattern necessary for controlling the reproduction of the data per unit is added as a preamble to the encoded recording data at a predetermined position. Thus, a recording code string is obtained (Step S803).
Here, the predetermined position of the encoded recording data is a position determined while taking into account that the recording code strings are successively recorded/reproduced. Further, the preamble includes, for example, a gain control pattern used in learning for gain control with respect to the reproduction signal, a synchronization pattern used in bit synchronization processing and the like, and a separation pattern necessary for calculating a channel matrix that corresponds to a positional relationship between a plurality of reproducing heads and a plurality of tracks of one unit in a track width direction. Here, the plurality of tracks of one unit refers to a plurality of tracks that constitute one unit of signal processing for reproducing data. The synchronization pattern is also used as information for specifying a start position of the separation pattern or data for each track. Those patterns are created in consideration of a regularity of the code strings generated in the recording encoding sections 121-1, 121-2, and 121-3 of the multitrack recording encoding section 120.
After being imparted with desired timings in the output timing setting sections 141-1, 141-2, and 141-3 of the multitrack recording section 140, the recording code strings of the respective tracks are subjected to the recording compensation processing for optimization for recording onto the magnetic recording medium 2 in the recording compensating sections 144-1, 144-2, and 144-3.
After that, the recording code strings of the respective tracks are subjected to a voltage-to-current conversion in the recording amplifiers 147-1, 147-2, and 147-3 and transmitted to the recording heads W-1, W-2, and W-3, to thus be recorded onto the magnetic recording medium 2 by the recording heads W-1, W-2, and W-3 (Step S804).
Then, the recording operation per unit described above with respect to the magnetic recording medium 2 is repeated so that a plurality of units are recorded successively in a track running direction.
Next, a reproducing apparatus that employs the magnetic recording/reproducing system described above will be described.
FIG. 34 is a diagram showing a structure of a reproducing apparatus 900 that employs the magnetic recording/reproducing system described above.
As shown in the figure, the reproducing apparatus 900 includes a reproducing head array 210, a channel reproducing section 220, a signal separating section 230, a multitrack demodulating section 240, and a restoring section 260.
The reproducing head array 210 includes N (N=3) reproducing heads R-1, R-2, and R-3 that read out signals from the tracks recorded onto the magnetic recording medium 2. A head width and position of the reproducing heads R-1, R-2, and R-3 are determined so that the reproducing heads R-1, R-2, and R-3 are capable of reproducing signals from one or more adjacent tracks on the magnetic recording medium 2.
The channel reproducing section 220 includes N reproducing amplifiers 221-1, 221-2, and 221-3 that amplify the signals reproduced by the N reproducing heads R-1, R-2, and R-3 mounted to the reproducing head array 210, gain adjusting sections 224-1, 224-2, and 224-3 that control a gain so that output amplitude levels of the N reproducing amplifiers 221-1, 221-2, and 221-3 become predetermined values, and A/D converters 225-1, 225-2, and 225-3 that quantize the outputs of the gain adjusting sections 224-1, 224-2, and 224-3 into digital values of a predetermined bit width.
It should be noted that a lowpass filter for removing unnecessary high-frequency components may be provided immediately before the A/D converters 225-1, 225-2, and 225-3 as necessary.
Moreover, the gain adjusting sections 224-1, 224-2, and 224-3 may be disposed subsequent to the A/D converters 225-1, 225-2, and 225-3 instead of before. This is effective in a case where the bit widths of the A/D converters 225-1, 225-2, and 225-3 are to be used effectively or a structure of the gain adjusting sections 224-1, 224-2, and 224-3 is to be made a simple structure that takes into account the detection of the patterns included in the preamble.
The signal separating section 230 includes a synchronization signal detecting section 231 for detecting synchronization patterns from the outputs of the A/D converters 225-1, 225-2, and 225-3, and a signal separating processor 236 for specifying a start position of the separation patterns based on synchronization signals detected by the synchronization signal detecting section 231 and carrying out a channel estimation calculation and a signal separation calculation using the separation patterns, to thus separate a reproduction signal of each track from the reproduction signals of one unit reproduced by the plurality of reproducing heads R-1, R-2, and R-3.
The multitrack demodulating section 240 includes M equalizers 241-1, 241-2, and 241-3 that carry out equalization processing on the reproduction signal of each track separated by the signal separating processor 236, M PLLs 242-1, 242-2, and 242-3 that carry out bit synchronization based on the outputs of the equalizers 241-1, 241-2, and 241-3, M detectors 243-1, 243-2, and 243-3 exemplified by a Viterbi detector, for generating code strings by binarizing the reproduction signals of the respective tracks using bit synchronization signals generated by the PLLs 242-1, 242-2, and 242-3, M synchronization signal detectors 244-1, 244-2, and 244-3 that detect the synchronization patterns on the code strings from the binarized reproduction signals as the outputs of the detectors 243-1, 243-2, and 243-3, and M decoders 245-1, 245-2, and 245-3 that specify a start position of the data based on the synchronization patterns detected by the synchronization signal detectors 244-1, 244-2, and 244-3 and decode data strings from the code strings.
The restoring section 260 includes a data integrator 261 that couples the data of the tracks output from the M decoders 245-1, 245-2, and 245-3 of the multitrack demodulating section 240 by an operation opposite to that at the time of recording, to thus restore reproduction data 3.
FIG. 35 is a flowchart showing a flow of a unit reproduction operation of the reproducing apparatus 900. In the reproducing apparatus 900, signals are first reproduced from the plurality of tracks of one unit on the magnetic recording medium 2 using the N reproducing heads R-1, R-2, and R-3 capable of reproducing signals from one or more adjacent tracks (Step S901).
Next, after the output amplitude levels of the reproducing amplifiers 221-1, 221-2, and 221-3 are adjusted by the gain adjusting sections 224-1, 224-2, and 224-3, the outputs of the gain adjusting sections 224-1, 224-2, and 224-3 are converted into digital values by the A/D converters 225-1, 225-2, and 225-3 and output to the synchronization signal detecting section 231 (Step S902).
The synchronization signal detecting section 231 detects, for each of the outputs of the A/D converters 225-1, 225-2, and 225-3, a synchronization pattern to specify a start position of the separation pattern in the preamble and the like (Step S903).
Next, the signal separating processor 236 specifies the start position of the separation patterns based on the synchronization signals detected by the synchronization signal detecting section 231 and obtains a channel matrix that corresponds to the positional relationship between each of the reproducing heads R-1, R-2, and R-3 and the plurality of tracks of one unit in the track width direction by the channel estimation calculation using the separation patterns (Step S904). After that, the reproduction signals of the respective tracks are separated from the reproduction signals of one unit reproduced by the reproducing heads R-1, R-2, and R-3 using the channel matrix (Step S905).
After that, the data string is decoded from the reproduction signal of each track by the multitrack demodulating section 240 (Step S906), and the pieces of data of the tracks are coupled by the restoring section 260. Thus, reproduction data 3 is obtained (Step S907).